Function 12h    Alternate Select (EGA and after) 
entry   AH      12h 
	BL      10h     return EGA information 
		return  BH      00h     if color mode is in effect (3Dx) 
			        01h     if mono mode is in effect (3Dx) 
			BL      00h     if 64k EGA memory 
			        01h     if 128k EGA memory 
			        02h     if 192k EGA memory 
			        03h     if 256k EGA memory 
			CH      feature bits 
			CL      switch settings 
		20h     select alternate print screen routine 
		30h     select vertical resolution for text modes       (VGA) 
			AL      00h     200 scan lines 
			        01h     350 scan lines 
			        02h     400 scan lines 
		return  AL      12h if function supported 
		31h     enable/disable default palette loading    (MCGA, VGA) 
			AL      00h     enable default palette loading 
			        01h     disable default palette loading 
		return  AL      12h if function was supported 
		32h     enable/disable video addressing           (MCGA, VGA) 
			AL      00h     enable video 
			        01h     disable video 
		return  AL      12h if function was supported 
		33h     enable/disable default gray scale summing (MCGA, VGA) 
			AL      00h     enable gray scale summing 
			        01h     disable gray scale summing 
		return  AL      12h if function was supported 
		34h     enable/disable text cursor emulation            (VGA) 
			AL      00h     enable cursor emulation 
			        01h     disable cursor emulation 
		return  AL      12h if function was supported 
		35h     display-switch interface                        (PS/2) 
			AL      00h     initial adapter video off 
			        01h     initial planar video on 
			        02h     switch active video off 
			        03h     switch inactive video on 
			        80h     *undocumented* set system board video 
			                active flag 
			ES:DX   buffer (128 byte save area if AL = 0, 2 or 3) 
		return  AL      12h if function was supported 
		36h     video refresh control                           (VGA) 
			AL      00h     enable refresh 
			        01h     disable refresh 
		return  AL      12h     if function supported 
			BX      5500h   (used by ATI and TAXAN) 
			BX      5502h   (used by ATI and TAXAN)